Humoral immune responses to tumors occur in a relatively high frequency in (1, 2). This phenomenon was exploited to identify a variety of tumor-associated antigens (taa) by screening autologous expression libraries with serum from cancer patients (1). Several of these taa now serve as T cell antigens for the induction of anti-tumor CTL-responses in patients (3, 4). This preference for the cellular-, in most cases cytotoxic immune response as therapeutic strategy is now being reconsidered and novel vaccines are designed to also induce antibody responses. In part, this change of concept may have been influenced by the recent success of various monoclonal antibodies for tumor therapy such as trastuzumab (Herceptin) and bevacizumab (Avastin) (5). While these monoclonal antibodies had been specifically raised against targets of presumed oncological relevance, antibodies occurring in cancer patients, either spontaneously or upon vaccination form a different class of molecules the therapeutic significance of which had been difficult to assess. This is mostly due to the lack of straightforward experimental approaches for their isolation and subsequent characterization in vitro and in animal models of human cancer.
Thus, there is a need to overcome the above-described limitations and to provide a therapeutic and diagnostic antibody against antigens involved in cancer.